On Wed, Apr 29, 2020 at 05:46:46PM +0300, Dmitry Osipenko wrote: > 29.04.2020 16:57, Jon Hunter пишет: > > > > On 29/04/2020 13:35, Dmitry Osipenko wrote: > >> 29.04.2020 11:55, Thierry Reding пишет: > >> ... > >>>>> It's not "papering over an issue". The bug can't be fixed properly > >>>>> without introducing I2C atomic transfers support for a late suspend > >>>>> phase, I don't see any other solutions for now. Stable kernels do not > >>>>> support atomic transfers at all, that proper solution won't be backportable. > >>>> > >>>> Hm... on a hunch I tried something and, lo and behold, it worked. I can > >>>> get Cardhu to properly suspend/resume on top of v5.7-rc3 with the > >>>> following sequence: > >>>> > >>>> revert 9f42de8d4ec2 i2c: tegra: Fix suspending in active runtime PM state > >>>> apply http://patchwork.ozlabs.org/project/linux-tegra/patch/20191213134417.222720-1-thierry.reding@xxxxxxxxx/ > >>>> > >>>> I also ran that through our test farm and I don't see any other issues. > >>>> At the time I was already skeptical about pm_runtime_force_suspend() and > >>>> pm_runtime_force_resume() and while I'm not fully certain why exactly it > >>>> doesn't work, the above on top of v5.7-rc3 seems like a good option. > >>>> > >>>> I'll try to do some digging if I can find out why exactly force suspend > >>>> and resume doesn't work. > >>> > >>> Ah... so it looks like pm_runtime_force_resume() never actually does > >>> anything in this case and then disable_depth remains at 1 and the first > >>> tegra_i2c_xfer() will then fail to runtime resume the controller. > >> > >> That's the exactly expected behaviour of the RPM force suspend/resume. > >> The only unexpected part for me is that the tegra_i2c_xfer() runtime > >> resume then fails in the NOIRQ phase. > > > > From reading the changelog for commit 1e2ef05bb8cf ("PM: Limit race > > conditions between runtime PM and system sleep (v2))", this is the > > expected behaviour for runtime resume in the noirq phase. > > I'm curious whether there is a way to tell RPM that it's okay to do it > for a particular device, like I2C that uses IRQ-safe RPM + doesn't have > parent devices that need to be resumed. Been there, done that: http://patchwork.ozlabs.org/project/linux-tegra/patch/20191128160314.2381249-2-thierry.reding@xxxxxxxxx/ Thierry
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